1. SCT On-detector VCSELs
SCT On-detector VCSELs use older proton implant devices, not oxide implant (as in SCT/Pixel off-detector VCSELs and pixel on-detector).
Slower and higher threshold (hence obsolete)
Better reliability “Gold Standard for reliability”
Standard Truelight part with good reliability data
Safer packaging because
no glue used over VCSEL surface (fibre held above surface by plastic spacer).
no Infineon connector.
We performed accelerated aging test for irradiated VCSELs.
19/8/10
Tony Weidberg ATLAS VCSEL Meeting

2. Tony Weidberg ATLAS VCSEL Meeting
Lifetime Studies (1)
Lifetime tests for the proton implant VCSELs: NIM A 497 (2003) 294.
20 devices operated DC for 2534 hours at T=100C.
Use Weibull distribution for failure rates
If a=1 Poisson distribution. Use Truelight value a=1.7.
90% c.l. MTTF = 8990 hours.
19/8/10
Tony Weidberg ATLAS VCSEL Meeting

3. Tony Weidberg ATLAS VCSEL Meeting
Lifetime Studies (2)
Use Arrhenius equation:
Use Truelight measurement EA=1 eV.
Assume T~ 0C  AF = 
MTTF ~9 104 years.
Don’t expect high failure rate over 10 years operation but need to monitor performance …
19/8/10
Tony Weidberg ATLAS VCSEL Meeting

4. VCSEL Power Measurements
Monitor VCSEL power using p-i-n current in BOC (USA15).
19/8/10
Tony Weidberg ATLAS VCSEL Meeting

5. Tony Weidberg ATLAS VCSEL Meeting
VCSEL Power Stability
Higher temperature after cooling restart
Good stability
Stability in 2008/9 checked with Rxthresholds and was also ok.
19/8/10
Tony Weidberg ATLAS VCSEL Meeting

6. Tony Weidberg ATLAS VCSEL Meeting
VCSEL Deaths
From May ’10 configuration:
Dead RX links 1.27%
Combination of electrical and optical failures.
Predominantly during installation ”delayed infant mortality” probably because burn-in could not be performed at sufficiently high temperature.
1 death in 2010, none in 2009.
Live time of RX links
NRZ data so depends on L1 rate and occupancy.
Very limitted equivalent on-time so far.
Need more operational experience at higher L1 rate before we can conclude anything about the long term reliability of the on-detector VCSELs.
19/8/10
Tony Weidberg ATLAS VCSEL Meeting

7. Tony Weidberg ATLAS VCSEL Meeting
Expected Data Rates
3 months of testing would confirm survival up to 2015.
19/8/10
Tony Weidberg ATLAS VCSEL Meeting

8. Tony Weidberg ATLAS VCSEL Meeting
Stress Tests
Need to perform stress tests at RT for long periods of time to detect any unexpected damage mechanism with a low value of EA
Plan to perform stress tests using harnesses on SR1 sector.
47 barrel and 33 EC modules
Run in clk/2 mode  50% duty cycle
Operate continuously apart from when sector required for training.
Measure power
Use OSA for periodical checks for spectral narrowing.
Use 7 or 8 non-electrical functioning modules on detector in clk/2 for similar stress tests.
19/8/10
Tony Weidberg ATLAS VCSEL Meeting